Princeton University

School of Engineering & Applied Science

Organic Electronic Device Modeling with Gaussian Density-of-States

Professor Yvan Bonnassieux, Ecole Polytechnique
Engineering Quadrangle, B205
Thursday, June 18, 2015 - 11:00am

Charge carrier injection and transport are crucial steps in the operation of electronic devices. Both of them highly depend on the electronic structure of the semiconductor. For organic semiconductors with structural, hence energetic, disorder, a Gaussian Disorder Model (GDM) was proposed, which establishes that all states are localized, so that thermally-assisted tunneling and trapping occurs simultaneously. However, this model mainly focuses on the transport mechanisms, and the role of charge carrier injection is overlooked in its application to device modeling. In particular, it has been shown that a Gaussian Distribution Of State (GDOS) may lead the organic solid to behave as a degenerate semiconductor, thus resulting in reducing the injection barrier and increasing the charge carrier density at the electrode. Accordingly, a further analysis of the injection process is gaining in importance, particularly in the case of organic solar cells, which operate at low voltage, injection-limited, regime. In this communication, we investigate the effect of the electronic structure of organic the semiconductor on charge carrier injection, as well as the low voltage, current density-voltage J(V) characteristics of Organic Rectifying Diodes (ORDs) based on GDM. Two analytical models for the J(V) characteristics of ORDs under non-degenerate and degenerate approximation have been developed. The experimental J(V) characteristics of an ORD having Au/pentacene/Al structure are fitted by both analytical models. It is found that the data are better fitted by the degenerate model, with more physically-meaningful parameters such as variance of the DOS, injection barriers, and mobility.